1. Field of the Invention
The present invention relates broadly to the field of magnetic sensors and to techniques for biasing magnetic sensors. More particularly, the present invention concerns a magnetic sensor package comprising a magnetic sensor element biased by a magnetic field produced by a current carried on a coil of electrically conductive wire and controlled by a selected one or more resistors from a plurality of selectable resistors to achieve a desired biasing effect, wherein at least the magnetic sensor element and the coil are protectively housed within an encapsulant.
2. Description of the Prior Art
Magnetic sensors are used in a variety of applications, including, for example, current sensing, linear or rotary motion detection, wheel speed sensing, and media (e.g., inks, currency) detection. It is often necessary or desirable to bias the magnetic sensor to, for example, provide a reference or set a condition of operation. A well-known prior art technique for biasing the magnetic sensor involves repositioning a permanent magnet in close proximity to the magnetic sensor until the desired degree of bias or biasing effect is achieved, whereafter the permanent magnet is permanently affixed in the corresponding position.
Unfortunately, this and other prior art biasing techniques suffer from a number of problems and disadvantages, including, for example, that the final position of the permanent magnet is directly related to and dictated by the required bias. This can be particularly problematic when the necessary position of the permanent magnet is already occupied by another component, or when the necessary position is beyond the bounds of the sensor's housing or allotted space.
Furthermore, because the permanent magnet must be physically repositioned, initial biasing can only be performed by a human or by a robot capable of moving the permanent magnet with the necessary degree of care and precision. This can be undesirably inefficient and expensive.
Additionally, because the permanent magnet must be accessible in order to be repositioned, both the magnetic sensor and the permanent magnet cannot be provided in a single sealed housing. As a result, the components of the magnetic sensor are exposed to a potentially damaging ambient environment and hazards of use, including dust and moisture, that can adversely affect performance.
Due to the above-identified and other problems and disadvantages in the art, a need exists for an improved mechanism for or method of biasing a magnetic sensor.